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Published December 2000 | public
Journal Article

The Use of Ambient Measurements To Identify which Precursor Species Limit Aerosol Nitrate Formation


A thermodynamic equilibrium model was used to investigate the response of aerosol NO₃ to changes in concentrations of HNO₃, NH₃, and H₂SO₄. Over a range of temperatures and relative humidities (RHs), two parameters provided sufficient information for indicating the qualitative response of aerosol NO₃. The first was the excess of aerosol NH₄⁺ plus gas-phase NH₃ over the sum of HNO₃, particulate NO₃, and particulate SO₄²⁻ concentrations. The second was the ratio of particulate to total NO₃ concentrations. Computation of these quantities from ambient measurements provides a means to rapidly analyze large numbers of samples and identify cases in which inorganic aerosol NO₃ formation is limited by the availability of NH₃. Example calculations are presented using data from three field studies. The predictions of the indicator variables and the equilibrium model are compared.

Additional Information

© 2000 Air & Waste Management Association. Support for this work was provided by the Western States Petroleum Association.

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